1. Field of the Invention
The present invention relates to a vehicle control apparatus. In particular, the present invention relates to an apparatus which controls an object having a possibility that requests may interfere with each other.
2. Description of the Background Art
There has been recently shown an increasing tendency to mount, on one and the same vehicle, many kinds of movement control apparatuses for controlling the movement of the vehicle. On one and the same vehicle have been installed, for example, movement control apparatuses for a VSC (Vehicle Stability Control), a VDIM (Vehicle Dynamics Integrated Management), an ABS (Antilock Braking System), a TRC (TRaction Control), an operation-assisted control (such as a cruise control, a follow-up control and a pre-crush control), a navigation ganged speed change control and the like. These movement control apparatuses are directed to a drive system (such as an engine and an automatic transmission), a brake system (such as a brake) and a steering system (such as a steering wheel).
However, respective effects to be produced by the different kinds of movement control apparatuses have been not always implemented independently of each other. If anything, the effects possibly have interfered with each other. Therefore, it has been important to control an object to be controlled in satisfactory association and cooperation among a plurality of kinds of movement control apparatuses in a vehicle mounting thereon the movement control apparatuses.
For example, both of a drive force request for the drive system from the aforementioned movement control apparatus and another drive force request by the operation of an acceleration pedal by a driver have been directed to the control of the drive system, thereby possibly inducing a fear of an interference with each other. In such a case, mutually contradictory requests may be possibly input into the drive system.
One example of drive force control apparatuses in the conventional art is disclosed in Japanese Laid-Open Patent Publication No. 2002-161772. The drive force control apparatus has allowed a driver to hardly feel an insufficient acceleration performance and abnormality caused by occurrence of a dead band. The drive force control apparatus has controlled a shift-wise automatic transmission whose speed change shift is controlled on the basis of a speed change line, a map for setting a target drive force according to a vehicle speed and an acceleration pedaling quantity, and an engine whose output is controlled to become the target drive force, wherein the map is disposed per speed change shift and is switched according to the speed change shift.
With the drive force control apparatus, the map for determining the target drive force has been disposed per speed change shift, and further, it has been switched according to the speed change shift. As a consequence, an optimum target drive force can be set per speed change shift without any adverse influence of hysteresis during the speed change.
However, the speed change of the shift-wise automatic transmission has been determined on the basis of an opening degree of an acceleration pedal and a vehicle speed in the drive force control apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-161772, thereby raising problems, as follows. For example, in the case where a vehicle starts to climb a slope after the speed change shift of the automatic transmission is changed from a second shift to a third shift by increasing an opening degree of an acceleration pedal by a driver, the speed cannot be changed despite of an increase in drive force request until the driver depresses the acceleration pedal in excess of a down shift line. As a result, the target drive force cannot be achieved with a maximum generation drive force in the third shift, thereby inducing a possibility that the driver feels abnormality.
In the meantime, in a speed change control in association with a navigation device, the condition of a road (such as an up or down slope, a curve or an intersection), on which a vehicle travels, has been read from the navigation device in advance, so that an optimum shift control can be performed. It has been determined, for example, on an up or down slope, as to whether a road is an up slope or a down slope on the basis of the condition of the road from the navigation device, an opening degree of a throttle, a vehicle speed and the like. As a consequence, an unnecessary up-shift can be suppressed so as to achieve an optimum drive force on the up slope.
Even if the speed change is determined on the basis of the vehicle speed and the opening degree of a throttle in place of the opening degree of the acceleration pedal, as disclosed in Japanese Laid-Open Patent Publication No. 2002-161772, a drive force request by the movement control apparatus which performs the speed change control in association with the navigation device may be possibly contradictory to a drive force request by the driver. Such a problem is not taken in Japanese Laid-Open Patent Publication No. 2002-161772.
Furthermore, in the case where the speed change is determined on the basis of the speed change map consisting of the opening degree of a throttle and the vehicle speed, there have arisen problems, as described below. In the case of an internal combustion engine serving as a drive source for a vehicle, a generation torque has been increased as the opening degree of a throttle is increased. In either of the case where the drive force request from the movement control apparatus is increased and the case where the drive force request according to the operation by the driver is increased, the drive force could be basically increased by increasing the opening degree of a throttle. However, when the opening degree of a throttle becomes greater to some extent, the drive force generated in the internal combustion engine has been saturated in view of its characteristics. This signifies that the drive force is only slightly varied (that is, is not increased) even if the opening degree of a throttle is greatly varied. Consequently, if there is a drive force request for slightly increasing the drive force (which is either the drive force request from the movement control apparatus or the drive force request according to the operation by the driver), the opening degree of a throttle has been largely varied. As a result, the opening degree of a throttle on the speed change map has been largely varied accordingly, thereby inducing a possibility of a busy shift in which an up shift or a down shift is repeated.